linux-kernel - Re: [RFC PATCH v2 07/11] powerpc/mm/radix: Use KUEP API for Radix MMU

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Message-ID: <cbd84ca9-4337-658e-d834-25943f5f3753@c-s.fr>
Date:   Wed, 28 Nov 2018 10:46:21 +0100
From:   Christophe LEROY <christophe.leroy@....fr>
To:     Russell Currey <ruscur@...sell.cc>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Michael Ellerman <mpe@...erman.id.au>
Cc:     linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH v2 07/11] powerpc/mm/radix: Use KUEP API for Radix MMU

Sorry, I forgot to reset the author so the patch appears as coming from 
yourself.

Le 28/11/2018 à 10:27, Russell Currey a écrit :
> Execution protection already exists on radix, this just refactors
> the radix init to provide the KUEP setup function instead.
> 
> Thus, the only functional change is that it can now be disabled.
> 
> Signed-off-by: Russell Currey <ruscur@...sell.cc>
> Signed-off-by: Christophe Leroy <christophe.leroy@....fr>
> ---
>   arch/powerpc/mm/pgtable-radix.c        | 9 ++++++---
>   arch/powerpc/platforms/Kconfig.cputype | 1 +
>   2 files changed, 7 insertions(+), 3 deletions(-)
> 
> diff --git a/arch/powerpc/mm/pgtable-radix.c b/arch/powerpc/mm/pgtable-radix.c
> index 931156069a81..45aa9e501e76 100644
> --- a/arch/powerpc/mm/pgtable-radix.c
> +++ b/arch/powerpc/mm/pgtable-radix.c
> @@ -535,8 +535,13 @@ static void radix_init_amor(void)
>   	mtspr(SPRN_AMOR, (3ul << 62));
>   }
>   
> -static void radix_init_iamr(void)
> +void setup_kuep(bool disabled)
>   {
> +	if (disabled)
> +		return;
> +
> +	pr_info("Activating Kernel Userspace Execution Prevention\n");
> +
>   	/*
>   	 * Radix always uses key0 of the IAMR to determine if an access is
>   	 * allowed. We set bit 0 (IBM bit 1) of key0, to prevent instruction
> @@ -605,7 +610,6 @@ void __init radix__early_init_mmu(void)
>   
>   	memblock_set_current_limit(MEMBLOCK_ALLOC_ANYWHERE);
>   
> -	radix_init_iamr();
>   	radix_init_pgtable();
>   	/* Switch to the guard PID before turning on MMU */
>   	radix__switch_mmu_context(NULL, &init_mm);
> @@ -627,7 +631,6 @@ void radix__early_init_mmu_secondary(void)
>   		      __pa(partition_tb) | (PATB_SIZE_SHIFT - 12));
>   		radix_init_amor();
>   	}
> -	radix_init_iamr();
>   
>   	radix__switch_mmu_context(NULL, &init_mm);
>   	if (cpu_has_feature(CPU_FTR_HVMODE))
> diff --git a/arch/powerpc/platforms/Kconfig.cputype b/arch/powerpc/platforms/Kconfig.cputype
> index a20669a9ec13..e6831d0ec159 100644
> --- a/arch/powerpc/platforms/Kconfig.cputype
> +++ b/arch/powerpc/platforms/Kconfig.cputype
> @@ -334,6 +334,7 @@ config PPC_RADIX_MMU
>   	bool "Radix MMU Support"
>   	depends on PPC_BOOK3S_64
>   	select ARCH_HAS_GIGANTIC_PAGE if (MEMORY_ISOLATION && COMPACTION) || CMA
> +	select PPC_HAVE_KUEP
>   	default y
>   	help
>   	  Enable support for the Power ISA 3.0 Radix style MMU. Currently this
>